A Wireless Local Area Network (WLAN) allows users virtually unrestricted access to Internet Protocol (IP) services and data networks. The use of a WLAN is not limited to laptop computers and other computing devices, but is rapidly expanding to include cellular telephones, Personal Digital Assistants (PDA)s, and other small wireless devices supported by an external network or carrier. For example, a wireless device communicating via a cellular carrier may roam into a WLAN in a cyber-cafe or workspace. In this situation, the wireless device has access to the cellular system, but desires access to the WLAN. The WLAN access requires authentication. As the wireless device has already gained access to the cellular system, the need for further authentication is redundant. There is a need therefore, for a mechanism that allows a common authentication for access to a cellular system and to a WLAN. Further, there is a need for a common mechanism for generating encryption keys used during communications.